Conventionally, there has been practically used microchips (also referred to as micro analysis chips or micro fluid chips) or an apparatus called JAS (Micro Total Analysis Systems) using the microchips, wherein a fine flow fluid passage or a circuit is formed on a silicon or glass substrate by using fine processing technology and chemical reactions, separation, and analysis of a nucleic acid, a protein, and a liquid sample such as blood are conducted in a minute space. Such a microchip (also referred to as micro fluid chip) reduces the used amounts of samples and reagents and the discharge amount of waste fluid, thereby achieving a space-saving, portable, and inexpensive system.
A microchip is manufactured by attaching two members to each other, at least one of which is finely processed. Recently, a resin microchip has been proposed to facilitate low-cost production. More specifically, the resin microchip is manufactured by bonding a resin substrate having a fluid passage groove on the surface to a resin cover (e.g., a film) for covering the fluid passage groove. Through holes are formed at the ends of the fluid passage groove on the substrate across the thickness direction, for example. The substrate having the fluid passage groove on the surface is bonded to the cover with the fluid passage groove inside. The bonding allows the cover to function as a lid for the fluid passage groove, and thus the fluid passage groove and the cover form a fluid passage. Thereby, a microchip including a fluid passage inside is manufactured. The through holes formed in the substrate link the fluid passage to the exterior of the microchip, thereby allowing the introduction and discharge of a liquid specimen via the through holes.
In such a microchip, a reaction needs to be observed at a fixed position on a fluid passage even when the microchips are frequently replaced to be used. For this reason, as a technique for finding a position of an observation fluid passage, there has been recently developed a technique wherein a position finding groove is provided in a microchip and the position of the observation fluid passage is determined by scanning a light beam across the groove (e.g., see Patent Document 1). Alternatively, a position of an observation fluid passage can be determined by filling a positioning fluid passage provided at both sides of the observation fluid passage with a fluorescent substance, and identifying the position to determine the position of the observation fluid passage.